In general, polyimide resins have wide utility as electronic materials including protective materials, insulating materials and the like of liquid crystal displays and semiconductors because of their inherent high mechanical strength, heat resistance, insulating properties, and solvent resistance. Recently, applications as a material for optical communication such as a material for optical waveguide have been expected.
In recent years, developments in this field are remarkable and there have been required ever higher characteristics of materials used to meet the developments. More particularly, not only such materials are excellent in heat and solvent resistances, but also they have been expected to have a number of properties varying depending on the intended use.
As an especially important characteristic, mention is made of high transparency. For one of methods of realizing the transparency, it has been already reported that there can be obtained a polyimide having a relatively low degree of coloration and high transparency by subjecting an alicyclic tetracarboxylic acid dianhydride and an aromatic diamine to polycondensation reaction to obtain a polyimide precursor and imidizing the precursor to prepare a polyimide (see Patent Documents 1 and 2).
However, under the recent circumstances wherein there is demanding the use of a polyimide having high heat and solvent resistances and high transparency in the field of electronic materials using light, developments of a novel type of polyimide having excellent characteristics are demanded.
Further, for a method of realizing the transparency, there can be expected a polyimide having high transparency by subjecting an alicyclic tetracarboxylic acid dianhydride and an alicyclic diamine to polycondensation reaction to obtain a wholly alicyclic polyimide precursor and imidizing the precursor to prepare a wholly alicyclic polyimide.
However, the polyimide obtained from 1,2,3,4-cyclobutanetetracarboxylic acid-1,2:3,4-dianhydride (CBDA) that is typical of existing alicyclic tetracarboxylic acid dianhydrides and an alicyclic diamine is brittle and cannot be used as a film. Thus, there has never been found a film of a wholly alicyclic polyimide which ensures stable strength.
It will be noted that there is an instance where bis-1,1′-(cyclopropane-2,3-dicarboxylic acid anhydride) (hereinafter abbreviated as BCPDA) is synthesized by photoreaction of acetylene and maleic anhydride (see Patent Document 3).
However, there is no instance of synthesizing a polyamic acid or polyimide by use of BCPDA.
Patent Document 1:                JP-B 2-24294 (Claims)        
Patent Document 2:                JP-A 58-208322 (Claims)        
Patent Document 3:                U.S. Pat. No. 3,522,160 (1970)        